A wireless communication system, such as a third generation partnership project (3GPP) long term evolution (LTE) system, may use Discontinuous Reception (DRX) procedures to reduce battery power consumption of a User Equipment (UE) in the system. For example, a base station in the wireless communication system may configure a DRX cycle for a UE. A configured DRX cycle may include a DRX inactive time and a DRX active time. A DRX active time may include one or more subframes. During the DRX active time, the base station may transmit DL transmission to the UE. A DRX inactive time may include the subframes from the end of the DRX active time in the last DRX cycle to the beginning of the DRX active time in the current DRX cycle. During the DRX inactive time, the base station may not send any Downlink (DL) communications to the UE. Therefore, the UE may deactivate some components during at least a portion of the DRX inactive time to save battery power, and activate these components during the DRX active time to receive the DL transmission.
The DRX cycle may be configured for a UE in either a connected mode or an idle mode. For example, a UE in an idle mode may wake up during the DRX active time to receive a DL paging channel transmission from a base station. The DL paging channel transmission may be an Earthquake Tsunami Warning System (ETWS) message, a broadcast system information message, or a paging message directed to the UE. A UE in a connected mode may wake up during the DRX active time to receive an ETWS message or a system information change notification transmitted on the DL paging channel. A UE in a connected mode may also wake up during the DRX active time to receive a Physical Downlink Shared Channel (PDSCH) transmission.